Heavy oils and extremely heavy oils can be transported in pipelines only with difficulty under conditions of ordinary outside temperatures, because of their very high viscosity. In order to raise their mobility, they are, therefore, frequently mixed with low-viscosity crude oils or refinery cuts; such a mode of operation requires relatively high quantities of additives to obtain any marked improvement in flow. In addition, such a procedure is feasible only where light-oil fields exist at the same site, or where a refinery in the vicinity can deliver low-viscosity gasoline fractions.
Another method that has also been employed resides in supplying heat to the heavy oil to lower its viscosity and correspondingly to improve its fluidity; considerable amounts of heat must be expended for this purpose. Thus, it is necessary, for example, to heat a heavy oil of 10.3.degree. API, the viscosity of which at 20.degree. C. is 40,000 mPa(s), to a temperature of about 95.degree. C. to obtain a viscosity of about 100 mPa(s), a threshold value frequently required for oil transportation in pipelines (M. L. Chirinos et al., Rev. Tec. Intevep. 3 (2): 103 [1983]). This means extremely high financial outlays for equipping and supplying the pipelines, and a loss of 15-20% of crude oil, since the necessary amount of heat is customarily obtained by combustion of crude oil.
Another method for heavy oil transport resides in pumping the oil through the pipelines in the form of a more or less readily fluid emulsion. Since the viscosity of emulsions is determined quite predominantly by that of the dispersant, an oil-in-water emulsion is involved here. The oil-in-water emulsion is produced by adding water and emulsifier to the oil using shear forces. This mixture is then pumped into the pipeline. The emulsion is subsequently separated into oil and water in a settling tank, for example before entering the refinery. The thus-separated oil is introduced into the refinery. The emulsifier, or minimum concentration, should produce a stable, readily fluid oil-in-water emulsion with a very high proportion of oil. This naturally poses high requirements on the emulsifiers. High shear forces must likewise be avoided during emulsification since the danger exists of inversion into a water-in-oil emulsion, extremely highly viscous in the case of crude oils. Furthermore, the emulsions should be stable with respect to relatively high salinities which occur in many deposit systems, as well as with respect to elevated temperatures. Further, despite exhibiting adequate stability while flowing through the pipeline, the emulsions should be separable again with minimum problems. Sulfur-containing emulsifiers are undesirable unless it is possible to maintain them in the aqueous phase during the separating step.
The emulsifiers proposed heretofore do not as yet adequately fulfill the aforementioned conditions. In many cases (for example, U.S. Pat. Nos. 4,285,356, 4,265,264 and 4,249,554), emulsions have oil contents of merely 50%; this means that half the pipeline volume is unavailable for actual oil transport. In other instances (for example Canadian Pat. Nos. 1,108,205, 1,113,529, 1,117,568, as well as U.S. Pat. No. 4,246,919), the reduction in viscosity attained by the addition of emulsifier is small, despite the relatively low oil proportion. And, finally, undesirable emulsifiers based on sulfur are frequently utilized.